1. Field of the Invention
This invention relates to a process and apparatus for cooking non-cured food products, including meat, poultry and fish, using direct-fired burners in a manner which prevents pink discoloration.
2. Description of Prior Art
When direct-fired burners are used for cooking non-cured meat, poultry, or fish products, a pink discoloration or ring is generally observed on the outer edges of the product being cooked. This pink discoloration is often objectionable to the consumer because it suggests that the meat, poultry, or fish is undercooked or contaminated. This pink color is only objectionable in non-cured meat, poultry, or fish products, and is not objectionable in cured meat or poultry such as ham, turkey, bacon, and corned beef in which the pink xe2x80x9ccuredxe2x80x9d color is intentionally created by adding sodium nitrite to the product mixture during processing. The sodium nitrite creates a chemical reaction which cures the product and turns the entire cross-section of the cooked product a pink color. This cured pink color is characteristic of all cooked and cured meat, poultry, and fish products. U.S. Pat. No. 5,443,852 teaches a proteinaceous food product containing stabilized cooked cured-meat pigment as a substitute for the use of nitrites to produce a product having the typical pink color of a nitrite-cured product.
The common belief is that in non-cured meat, poultry, and fish products, the primary cause of the pink discoloration is either nitric oxide (NO), or carbon monoxide (CO), or both, from the exhaust of direct-fired burners. It is believed that these gases are absorbed into the surface of the non-cured product, that they then combine with the product pigments and, when heated, form the pink discoloration. We have determined, through experimentation on an industrial forced air convection oven with direct-fired natural gas burners that neither NO nor CO are the cause of the pink discoloration. Rather, we have found that nitrogen dioxide (NO2) from the direct-fired burner is the only cause of this pink discoloration. Accordingly, by controlling the level of NO2 in the atmosphere in which the non-cured meat, poultry, or fish product is cooked, we can eliminate the pink discoloration. It should also be noted that other forms of NOx do not appear to contribute to the formation of pink discoloration during the cooking process.
Accordingly, it is an object of this invention to provide a process for cooking non-cured food products including non-cured meat, poultry, or fish products in a manner which does not produce the pink discoloration which is so objectionable to consumers.
It is another object of this invention to provide an apparatus suitable for carrying out the cooking process by which the formation of pink discoloration is eliminated during the cooking of non-cured food products.
These and other objects of this invention are achieved by a process for cooking non-cured food products, typically meat, poultry, fish and combinations thereof comprising heating the non-cured food products in a direct-fired oven and generating and maintaining an atmosphere in said direct-fired oven comprising less than about 0.5 volumetric parts per million dry (vppmd) of NO2. We have found that maintaining the level of NO2 in the direct-fired oven below about 0.5 vppmd prevents the formation of pink discoloration during cooking in non-cured food products.
An apparatus for cooking non-cured food products such as meat, poultry, fish and combinations thereof in accordance with this invention comprises a heating chamber, direct-fired means for heating the interior of the heating chamber, said direct-fired means in communication with the heating chamber, and atmosphere control means for producing and maintaining an atmosphere comprising less than about 0.5 vppmd of NO2 in the heating chamber.
In accordance with one preferred embodiment of this invention, the atmosphere control means comprises a direct-fired burner, the combustion from which produces less than about 0.5 vppmd of NO2. In accordance with another embodiment of this invention, the atmosphere control means comprises dilution means for diluting the products of combustion from said direct-fired burner, thereby reducing the concentration of NO2 in the heating chamber.